1. Field of the Invention
The invention relates to teeth implants made of metal.
2. Prior Art
There are implants made of metal to anchor superstructures made up of one or more crowns or parts of crowns, also containing metal, in the form of bridges. The implant consists of an actual implant body which is embedded in the jaw and a part bearing the superstructure which sets up the connection between the actual implant body and the superstructure and is surrounded by the mucous membrane. Implants of such type have been known for quite a long while and are available in various forms. The forms of the actual implant body can be screws or forms which are derived from screws. They also can be shaped like leaves or, as has recently been suggested, they can have the form of hollow cylinders. Such implants consist of another part, in addition to the actual implant body, which provides connection with the oral cavity through the mucous membrane. Such part can either be connected with the implant body to form a single piece or it can be screwed onto the actual implant body, sometimes only later and in a second operation, or can be fastened to it in some other way. The superstructure is placed on this part of the implant that projects into the oral cavity. This superstructure can either consist of a single crown or of a bridge, which then usually holds several crowns. If that is the case, the implant serves as a bridge support.
In most metal implants up to the present, an electrically conductive connection exists between the actual implant body and the part bearing the superstructure and the crown. If different metals occur at any place in this overall construction, an electrical element is formed in working together with the saliva which functions as an electrolyte and the adjoining tissue parts which also function as electrolytes. Since, in general, and with most of the known implants, only one metal is used in the implant itself and its component parts, the metal used in the crown will be the chief cause of the formation of this galvanic cell in this general case. The occurrence of such galvanic cells in the mouth area is particularly harmful when a part of the flow of current caused by this cell passes through the tissue of the mucous membrance and the adjoining bone. Specifically, a polarization of the cell membranes occurs then which can bring about pathological changes. Furthermore, a transfer of material can occur which brings about a shift in the equilibrium of the concentrations so that optimum physiological conditions no longer prevail in all areas of the tissue adjoining the surface of the implant. This, in turn, can bring about degeneration of the tissue in the immediate neighborhood of the implant from which a contribution to premature loss of the implant may occur. Naturally, this effect is especially likely to have drastic consequences when several implants are connected by bridge structures, since electric currents will then flow through large areas of the jaw in a completely unphysiological manner.
A solution to this complex problem is available through the use of ceramic implants, that is, non-conductive implants. However, there are cases in which metal implants have to be used for reasons of size and mechanical stability. This is made possible by the fact, among other things, that there are metals which have similar qualities of compatibility whith various substances, as is the case, for example, with extremely pure aluminum oxide, ceramics that are resistant to breaking. The most important metal that satisfies this requirement is titanium. Some alloys with a high titanium content are also suitable.